Publication DE-A1-43 26 802 discloses a fuel lance, for spraying liquid or gaseous fuels into a combustion chamber. The fuel lance is part of an secondary or tertiary burner, around which a combustion air jet flows in a main flow direction, and comprises inside an outer lance shell a liquid-fuel passage for supplying liquid fuel, a gas passage surrounding the liquid-fuel passage and intended for supplying gaseous fuel, and an air passage surrounding the gas passage and intended for supplying cooling or atomizing air, and first means for the radial spraying of the liquid fuel from the liquid-fuel passage into the combustion chamber, and second means for the radial spraying of the gaseous fuel from the gas passage into the combustion chamber see publications U.S. Pat. Nos. 5,431,018, 5,626,017 and EP-A1-0 620 362). In this case, the nozzles for gaseous fuel and liquid fuel (oil, etc.) are combined.
In the publication referred to, the spraying of the liquid fuel is effected according to the so-called air-blast principle, i.e. the fuel applied as a film to an atomizer lip is atomized in the shearing zone of the surrounding air flow and is admixed to the combustion air as a fuel mist. If the spraying is effected transversely to the flow direction of the combustion air, the penetration depth is determined solely by the air impulse. The natural impulse of the liquid fuel is merely utilized for producing the film but not for assisting the fuel jet.
To produce as homogenous an air/fuel mixture as possible, it is necessary for the fuel from the wake of the nozzle to be distributed in the cross section of the combustion air. During high transverse flows, a correspondingly high jet impulse is necessary. This high jet impulse cannot be achieved with the atomizing air alone. Therefore the natural impulse of the sprayed liquid fuel (or the gaseous fuel) is to be utilized in an assisting manner. The disintegration of the fuel jet is effected by jet instabilities after a few jet diameters of running length.